Outlook 2007 attachments in Vista loose file extension with "Save As"

I've come across two PC's with the following issue:
Running Windows Vista and Outlook 2007, when right-clicking a file attachment in an email and selecting "Save As..." the file extension is getting lost, saving a .pdf or any other file type as a .[nothing].

In the Save As... explorer box that appears the File Type is showing "All Files" and has no other options on the systems on which this is occurring, which is not all of the available Vista+Office 2007 systems here.

Any thoughts? The current work-around is to double-click the attachment to open it in the corresponding application (word, excel...) then save the file, as that works without any problems.

OK, the issue came up with a second user today which is why I posted the issue, however it appears my recollection of the first time was off, and missed similar details of the second occurence. It would seem on both occurrences it only occurs when the users are renaming the file, and they were deleting the extension, or retyping the entire file name without re-adding the extension.

So the extension was the issue, however the behavior is different than it used to be - Outlook 2003 would know the file type so when you renamed the file and saved it would still save it as the correct file type with no need for the user to keep the file type extension in the filename field. Can the previous behavior be restored, as I see this as becoming a more widespread issue as Vista machines become more prevalent in my environment.

To clarify my updated and more accurate description of my issue: Outlook is not "knowing" the "Save as type" for the file type on some machines, but not all. On my own vista the Save as Type is working - knowing the file type, and thus keeping it should I rename the file when saving even if I delete the file extension. On others, only "All files" is available in the Save as type field, thus loosing the file extension if not kept in the file name field.